WebView.CanGoBack on Windows Returns true When it Shouldn't

### Description

This is a separate report of issue "d" on #10814.

The relevant code is:

``` C#
if (webView.CanGoBack)
webView.GoBack();
else
Shell.Current.Navigation.PopAsync();
```

Unfortunately, under some circumstances on Windows CanGoBack always returns true.

### Steps to Reproduce

To reproduce it use the flyout to show help, then click a link to show the index, clicking the "back" arrow will move to the initial help page as expected, but doing the same thing a second and subsequent time will just show the same help page again and again on Windows because CanGoBack always returns true.

For more detailed instructions see #10814.

### Link to public reproduction project repository

https://github.com/david-maw/MauiHelp.git

### Version with bug

11.0.0-preview.6

### Is this a regression from previous behavior?

Not sure, did not test other versions

### Last version that worked well

_No response_

### Affected platforms

Windows

### Affected platform versions

Windows 11

### Did you find any workaround?

I tested this on NET 11 Preview 7, but it's an old bug.

### Relevant log output

```shell

```

Start with the WebView.CanGoBack, WebView.GoBack, and Shell.Current.Navigation.PopAsync entry points described in the issue, then run the linked MauiHelp reproduction on Windows 11. Reproduce the repeated back-arrow behavior and trace why CanGoBack remains true; done means back navigation returns to Shell navigation after the history is exhausted.

Written by the indexing model from the issue text.